Experimental investigation of the thermal performance of functional magnetic nanofluids

• Main Author: Lim, Zheng Hong
• Other Authors: Wong Teck Neng
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Nanotechnology; Engineering::Aeronautical engineering
• Online Access: https://hdl.handle.net/10356/141440
• Institution: Nanyang Technological University

This Final Year Project aims to find out the effect on heat transfer performance of the base fluids when nanoparticles are added. The project also seeks investigate if the by products from the purification process of carbon nanotubes (CNT) can be used as nanoparticles. Lastly, the effects of addition of nano magnetic stir bar into nanofluids were also studied. The Linear Heat Conduction Unit and the convective test cell were utilised to test the thermal conductance and the convective heat transfer coefficients of the nanofluids respectively. Experiments were done with Linear Heat Conduction Unit using different fluids. The tests showed that viscosity played a vital part in the heat transfer properties of the fluid. There is an inverse relationship between the thermal conductivity and the viscosity of the fluid. Test with the Linear Heat Conduction Unit, using polyethylene glycol (PEG) base nanofluids at different concentration found that the highest concentration nanofluid have the highest improvement in thermal conductance in comparison to the base fluid, PEG. The effects resulting from aggregation of nanoparticles in nanofluid were also studied. Experiments were also done using the convective test cell using water and water based nanofluids. The tests indicated that these nanofluids have lower convective heat transfer coefficient when measured against water. Nanofluids with nano stir bars were added to the test cell and placed between rotating magnets. The convective heat transfer coefficient of the nanofluid improved, suggesting the addition of magnetic nano stir bar has led to improvement in the heat transfer performance. The rotation speed of the magnets was increased leading to higher convective heat transfer coefficient. However, some this improvement in thermal properties is likely a result of vibration caused by rotating magnets. All in all, PEG based nanofluid shows the best improvement in thermal conductance when compared to water or thermal paste. The performance is likely a result of lower viscosity of PEG based nanofluid. There is also an improvement in convective heat transfer coefficient as nanomagnetic stir bars were added into nanofluids. The vortices generated from the stir bars in the nanofluid likely improved the thermal performance. Therefore, the results are promising. Nonetheless, more tests and studies need to be conducted to gain a better comprehension of the thermal performance of nanofluids to maximise its potential.